The present invention relates to a device for electroplating of disc elements, such as matrices for audio and video discs, said device comprising a housing for an electrolyte bath, the disc element being clampable in the housing in such a manner that the disc side to be plated can be in contact with the electrolyte bath while its other side is kept sealed from the electrolyte bath, and a means arranged to abut against the disc element to transmit electrical current thereto during the plating process.
In electroplating of matrices for audio and video discs it is of great importance that the current transmission to the matrix be as evenly distributed as possible around the periphery of the matrix to thereby achieve a plating layer, the thickness of which is as even and uniform as possible.
A previously known device for this purpose comprises a central hub from which there extend essentially radially a plurality of electrically conducting elements, such as antennae, strips of sheet metal or sheet metal in the form of circle sectors, which, at their distal ends, are resiliently in contact with one side of the matrix at its outer peripheral area. Thus, a certain number of contact points are obtained distributed around the periphery of the matrix. One problem which can occur in such a design is that current concentrations can be formed at the contact points between the electrically conducting elements and the matrix disc, as a result of microstructural uneven areas in the matrix disc, which can create bums in the disc and thus unevenness in both the disc and the layer thickness in the surface coating obtained.
JP-A-63-134 688 shows a device for producing a press matrix, with a plating carried out on a metal layer with signal information on a glass substrate. An elastic, electrically conducting central washer is placed on the electrolyte bath side and conducts current to the central portion of the metal layer without damage thereto when the center screw is tightened.